The present invention relates to an electrical machine having a first component (for example a rotor) and a second component (for example a stator), which is magnetically coupled to the first component and can be moved in a movement direction with respect to the second component. The electrical machine furthermore has a magnet pole arrangement on the first component, whose poles are aligned in the movement direction alternately on the one hand in a first magnetic field direction and on the other hand in a second magnetic field direction, which is opposite to the first magnetic field direction. In this case, a boundary between poles of different magnetic field directions runs corresponding to a first skew angle in a first area of the first component and corresponding to a second skew angle relative to the movement direction in a second area of the first component. The present invention relates in particular to rotating or linear electric motors.
The shape of the excitation field has a major influence on the operating behavior of an electrical machine with permanent-magnet excitation. In this case, a greater or lesser force ripple and torque ripple can always be observed. The aim is to minimize this, at the same time as maximizing the torque.
One effective means for improving the torque ripple is to skew the stator and/or rotor through, for example, one slot pitch. FIG. 1 shows a skew such as this using the example of a rotor whose outer surface is unrolled in the illustration shown in the drawing. Half the circumference πr is therefore illustrated in the vertical direction. In particular, the rotor has a length l in the axial direction. Permanent magnets or poles with different magnetic field directions or magnetization directions are arranged on the rotor surface. These magnetization directions are symbolized in FIG. 1 by N and S. Boundaries G1, which indicate the possibly continuous transition for example from a north pole N to a south pole S, run between the poles of different magnetization directions.
The rotor moves in a movement direction B with respect to the stator. The boundaries G1 run essentially transversely with respect to the movement direction B and assume an axial skew angle β with respect to the perpendicular to the movement direction. The axial skew angle leads to an arc ar over the overall length l of the rotor, where a represents the center angle and r the radius of the rotor.
Electrical machines with excitation fields which are characterized by an axial skew angle β such as this are prior art. Furthermore, electrical machines are also known with rotors in which the rotor is subdivided transversely with respect to the movement direction B, that is to say in the axial direction, into two areas A1 and A2, as is sketched schematically in FIG. 2. Furthermore, rotors are also in use which are subdivided in the axial direction into four sections A1, A2, A3 and A4, as shown in FIG. 3. The respective section length is ½ or ¼. The axial skews or boundaries G2, G3 in this case run linearly in sections. Corresponding to the example shown in FIG. 2, this results in an axial skew angle β1 in the section A1, and an axial skew angle β2 in the section A2. β1=−β2, that is to say |β1|=|β2|. In the example shown in FIG. 3, the axial skew angles also have identical magnitudes to one another. The document DE 101 47 310 B4 discloses magnets which allow discrete magnetization in a plurality of sections, as in FIG. 2 or 3.
The object of the present invention is to further reduce the force and torque ripple of an electrical machine.
According to the invention, this object is achieved by an electrical machine having a first component, a second component, which is magnetically coupled to the first component and can move in a movement direction with respect to the second component, and a magnet pole arrangement, which is formed on the first component and whose poles are aligned in the movement direction alternately on the one hand in a first magnetic field direction and on the other hand in a second magnetic field direction, which is opposite to the first magnetic field direction, wherein a boundary between poles of different magnetic field directions runs corresponding to a first skew angle in a first area of the first component and corresponding to a second skew angle relative to the movement direction in a second area of the first component, and with the first skew angle having a different magnitude than the second skew angle.